Musannaf Ibn Abi Shayba 27:41

Umar ibn Sa'd Abu Dawud al-Hafari narrated to us, from Sharik, from al-Rukin, from al-Qasim ibn Hassan, from Zayd ibn Thabit, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, I am leaving among you the two successors after me: the Book of Allah and my progeny, the people of my house. And indeed, they will never separate until they return to me at the Basin."